All major textures in the game were increased to 400%+ of their original pixels, sharpened, and had some detail added. Then new normal maps were generated to take advantage of the greater detail, which results in a significant improvement over the original graphics. This enjoys 0% compression files, which helps offset the fact that larger files requires more system resources.
This will convert 2.0 to 3.0 adding all the altered textures as well as all the meshes. This will not help with 1.X versions so you will need to DL the full 3.0 (to get the new normal maps). Just install this over the previous version and overwrite when prompted.